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Chapter 5 Reliability Robert J. Drummond and Karyn Dayle Jones Assessment Procedures for Counselors and Helping Professionals, 6 th edition Copyright ©2006.

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Presentation on theme: "Chapter 5 Reliability Robert J. Drummond and Karyn Dayle Jones Assessment Procedures for Counselors and Helping Professionals, 6 th edition Copyright ©2006."— Presentation transcript:

1 Chapter 5 Reliability Robert J. Drummond and Karyn Dayle Jones Assessment Procedures for Counselors and Helping Professionals, 6 th edition Copyright ©2006 by Pearson Education, Inc. Upper Saddle River, New Jersey All rights reserved.

2 Reliability The degree to which test scores are consistent, dependable, and repeatable Does the test accurately measure what it's supposed to measure? Robert J. Drummond and Karyn Dayle Jones Assessment Procedures for Counselors and Helping Professionals, 6 th edition Copyright ©2006 by Pearson Education, Inc. Upper Saddle River, New Jersey All rights reserved.

3 Reliability Coefficients A measure is reliable to the extent that the score remains nearly the same on repeated measures, indicating a low standard error of measurement Correlation coefficient:.00 to indicates a lack of reliability; 1.00 indicates perfect reliability Robert J. Drummond and Karyn Dayle Jones Assessment Procedures for Counselors and Helping Professionals, 6 th edition Copyright ©2006 by Pearson Education, Inc. Upper Saddle River, New Jersey All rights reserved.

4 Methods of Assessing Reliability Test-Retest: Stability Alternative Forms: Equivalence and Stability Split-Half Reliability: Equivalence and Internal Consistency Kuder-Richardson: Internal Consistency Robert J. Drummond and Karyn Dayle Jones Assessment Procedures for Counselors and Helping Professionals, 6 th edition Copyright ©2006 by Pearson Education, Inc. Upper Saddle River, New Jersey All rights reserved.

5 Methods of Assessing Reliability Test-Retest: give the same test twice, then correlate the two sets of scores to obtain a test-retest coefficient. Provides a coefficient of stability. Alternate Forms: administer two equivalent forms of a test, then correlate the scores to provide an estimate of reliability. Provides a coefficient of equivalence and stability. Split-Half Reliability: administer one test, then divide the test into two comparable halves. A coefficient is calculated between the two halves. Provides a coefficient of equivalence and internal consistency. Kuder-Richardson: compute the reliability of test items to each other and to the total test. Provides measure of internal consistency. Robert J. Drummond and Karyn Dayle Jones Assessment Procedures for Counselors and Helping Professionals, 6 th edition Copyright ©2006 by Pearson Education, Inc. Upper Saddle River, New Jersey All rights reserved.

6 What do these reliability coefficients mean? The test-retest reliability correlation of the midterm after a 3-week interval is.85. The alternate forms reliability correlation of the midterm is.52. The split-half forms reliability correlation of the midterm is.30. The internal consistency reliability of the midterm is.40. Robert J. Drummond and Karyn Dayle Jones Assessment Procedures for Counselors and Helping Professionals, 6 th edition Copyright ©2006 by Pearson Education, Inc. Upper Saddle River, New Jersey All rights reserved.

7 Inter-rater Reliability Measures homogeneity. Used to assess the degree to which different raters/observers give consistent scores on the same rating instrument. Robert J. Drummond and Karyn Dayle Jones Assessment Procedures for Counselors and Helping Professionals, 6 th edition Copyright ©2006 by Pearson Education, Inc. Upper Saddle River, New Jersey All rights reserved.

8 Standard Error of Measurement A measure of the "spread" of a person’s scores had the person been tested repeatedly. If an individual were to take the same test repeatedly (with no new learning taking place between testings and no memory of test items/answers), the standard deviation of his or her repeated test scores is denoted as the standard error of measurement. Tells the range within which a person’s true score may fall. Robert J. Drummond and Karyn Dayle Jones Assessment Procedures for Counselors and Helping Professionals, 6 th edition Copyright ©2006 by Pearson Education, Inc. Upper Saddle River, New Jersey All rights reserved.

9 Factors Influencing Reliability Length of the test: the longer the test, the higher the reliability Reliability of scoring: multiple-choice tests are more reliable than essay tests Variability of group: the more homogeneous the group, the lower the reliability Difficulty of test items: reliability is lower when the test is either too easy or too difficult A common set of instructions A common environment in which to attempt the test The scoring procedure of the test Robert J. Drummond and Karyn Dayle Jones Assessment Procedures for Counselors and Helping Professionals, 6 th edition Copyright ©2006 by Pearson Education, Inc. Upper Saddle River, New Jersey All rights reserved.


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